The present invention relates generally to valves and more particularly to a valve with an improved bearing support and seal combination. Valves of the aforementioned type are often used as a fuel valve and controller for gas turbines. If this valve should fail for any reason, it is an extremely expensive process to stop the gas turbine and replace the fuel valve. Accordingly, it is very important to have a valve in such application which will operate effectively, require low operating torque, provide an effective main valve seal, and have a long life.
One of the problems with the prior art is that after only a short period of use, the valve rotor has been known to lock up, rendering the valve inoperable. If the clearance between the rotor and cartridge is increased to prevent lock-up, flow will continue through the valve even when the valve is in the closed position.
Therefore, one of the necessary features of such a valve is to have a high turn-down ratio, meaning essentially the ability to control the flow and stop the valve from leaking as the rotor approaches the closed position. This requires the valve parts to be made with very close tolerances. These close tolerance requirements increase the expense of manufacture and also cause the valve to wear out sooner than is desired because of galling between the mating surfaces and/or being more susceptible to dirt particles which wear out the sealing surfaces and the bearing surfaces. Additionally, if these sealing and bearing surface areas are small mating parts they will wear out sooner than if a larger sealing or bearing surface is used.